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Screw Tip to Screen Changer

Modified on Saturday, 31 January 2015 03:03 PM by mpieler Categorized as Consultants Corner
Screw tip to screen changer
Vol. 20 #3, December 1993

When adding an automatic screen changer to a new or existing extruder, the screw needs to extend into the screen changer body to eliminate the existence of additional material inventory, which will require additional soak time during start-ups. The screw should be extended to within 1/4" to 3/8" of the breaker plate. The amount of extension can be supplied by the screen changer manufacturer. Any screw manufacturer can make the modification to an existing screw by making a threaded extension, or to have the additional length added as an integral part of a new screw. The new extension should be either non flighted or, preferably, flighted with the extended portion of flights undersize from the main flight diameter by .015 to .020" per side. The reason for the non-flighted or undersizing of the flights in the extended area, is that the entrance bore of the screen changer is not hardened like the barrel liner, and the flights will gall in the bore of the screen changer.

- Tim Womer

See also:
  • Are you a candidate for a continuous screen changer?
  • How to buy a screw - Part II
  • Polymer filtration II

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